This invention relates to a ball bearing swivel of the type which comprises a substantially bowl-shaped casing member having connection means in its closed end, and a stud member which has second connection means in that one of its ends which faces away from said casing member and in its other end a shank member which by means of a ball or roller bearing is journalled substantially undisplaceably in the direction of the rotational axis of the swivel in the bowl-shaped housing member. Such swivels are utilized to make possible mutual rotation between two interconnected members, e.g. a crane hook with a load suspended therein and a chain or wire, in which the hook is suspended. Swivels of this general kind which may be either of the ball bearing type or the slide bearing type have long been known. An example of such a ball bearing swivel forms the subject matter of the U.S. Pat. No. 2,384,490.
It is also known (U.S. Pat. No. 2,897,257) to insulate a crane hook from the wire, chain or the like in which the hook is suspended through an insulating link or connection member which is interposed between the hook and the wire. The object of the insulating link is primarily to prevent a person who with or without purpose contacts the hook or an electrically conducting object suspended therein from being subjected to a dangerous electrical shock if the electrically conducting wire or the like, in which the hook is suspended, should get into contact with a high-voltage electrical overhead line. Other devices of a related kind are disclosed in the U.S. Pat. Nos. 2,740,000 and 3,764,169.